Bandit Alley

MODEL SPECIFIC => SUZUKI BANDIT 250 & 400 => Topic started by: digitaldan on March 15, 2008, 04:55:24 PM

Title: What causes a 400 to run rich ?
Post by: digitaldan on March 15, 2008, 04:55:24 PM
Ok guys I have some questions on the GSF400. I run at 5000 feet above sea level, the mainjets are 87.5 so not too big. The exhaust continues to have lots of black carbon in it. I even removed the air filter completely to test and still had some carbon in the pipe. It uses no oil but black smoke can be seen sometimes after startup from cold. As it warms up it's easy to stall the bike when pulling away, in cooler weather it's much better. So if it's not the air filter and not mj's being too big what else can I try ? Carb rebuild ? Incorrect fuel supply ? My bike is a 1995 GSF400VV with 11 000 miles. It has some minor rust in the tank as well.

Apreciate any info  :thanks:
Title: Re: What causes a 400 to run rich ?
Post by: Banditmax on March 15, 2008, 05:19:29 PM
leaking o rings and worn needle jets are the commonest causes.
Title: Re: What causes a 400 to run rich ?
Post by: gsxr400 racer on March 16, 2008, 07:24:32 PM
Take care of the rust in the tank and rebuild the carbs
Title: Re: What causes a 400 to run rich ?
Post by: Thief400 on March 17, 2008, 10:46:14 PM
Check to see if the cold start plungers are closing all the way when you turn the choke off
Title: Re: What causes a 400 to run rich ?
Post by: gsxr400 racer on March 18, 2008, 12:13:35 AM
Check to see if the cold start plungers are closing all the way when you turn the choke off
And another great one and often over looked before removing the carbs :beers:
Title: Re: What causes a 400 to run rich ?
Post by: Forde on March 18, 2008, 06:08:29 PM
My exhaust has some black in it...

However the bike runs well, doesnt foul plugs, doesnt have any flat spots, and doesnt smoke, so im happy enough!!  With my race pipe on i should be getting flat spots and lean running going by what is said on here...  Maybe the previous owner jetted the bike, i dunno...
Title: Re: What causes a 400 to run rich ?
Post by: Banditmax on March 18, 2008, 06:40:33 PM
I get black on my exhaust too. Got another set of carbs im building up at the moment and will see if they help.
Title: Re: What causes a 400 to run rich ?
Post by: digitaldan on April 05, 2008, 05:20:24 PM
I really have no experience on these carbs. The other day when I was riding to work the bike went to three cylinders while doing 70 mph ! Can it be running so rich ? No I've been thinking the spark plugs may need replacing. Maybe they are the originals from the mid 90's and they can't deliver the needed spark anymore. I had a VFR 400 that sat for a long time and it's plugs were finished. Also would apreciate more info as to where I will find the cold start plungers. I rarely use the choke, I rather open the throttle slightly when cold.
Title: Re: What causes a 400 to run rich ?
Post by: gsxr400 racer on April 05, 2008, 05:57:03 PM
as in the choke plungers? your local dealer
Title: Re: What causes a 400 to run rich ?
Post by: Vanishing_Point on April 09, 2008, 12:56:37 PM
Check to see if the cold start plungers are closing all the way when you turn the choke off
And another great one and often over looked before removing the carbs :beers:

Hmm, I think mine may not be closing completely too. How would you remedy this? Lube the choke cable or something?
Title: Re: What causes a 400 to run rich ?
Post by: gsxr400 racer on April 09, 2008, 01:40:33 PM
yes lube the cable and you can pull the plungers out and polish them up with some metal polish.
Title: Re: What causes a 400 to run rich ?
Post by: yuckhil on April 14, 2008, 02:44:42 AM
Check to see if the cold start plungers are closing all the way when you turn the choke off

I think I need to check this too.  Could I possibly get a bit of description on where to locate the plungers?  I've never taken the tank off before, but I figure this is as good a time to start as any, since the local mechanics are really screwing me around.

yes lube the cable and you can pull the plungers out and polish them up with some metal polish.

Once the tank is off, will I see/access them directly by finding the end of the choke cable?

Apologies for the newbie questions and thanks.
Title: Re: What causes a 400 to run rich ?
Post by: gsxr400 racer on April 14, 2008, 11:24:23 AM
Check to see if the cold start plungers are closing all the way when you turn the choke off

I think I need to check this too.  Could I possibly get a bit of description on where to locate the plungers?  I've never taken the tank off before, but I figure this is as good a time to start as any, since the local mechanics are really screwing me around.

yes lube the cable and you can pull the plungers out and polish them up with some metal polish.

Once the tank is off, will I see/access them directly by finding the end of the choke cable?

Apologies for the newbie questions and thanks.

once the tank is off you will have to remove the carbs to do the plungers but while the cable is still attached move the lever to see the bracket move that connect all 4 choke plungers.
Title: Re: What causes a 400 to run rich ?
Post by: yuckhil on April 27, 2008, 02:45:08 AM
Thanks mate.  Turns out the oil level was too high.  Damn city workshops!  :taz:
Title: Re: What causes a 400 to run rich ?
Post by: andrewsw on April 27, 2008, 05:54:54 PM
another common cause of richness.. though it's easy to spot because the darn thing won't run hardly at all at low revs... stuck float or bits of debris in the float valve causing the float bowl to overflow into the cylinder. If it's a small enough bit of debris, it will just cause it to idle poorly or bog down and misfire when decelerating. Typical symptoms -- fouled plug in one cylinder, clears up when revved, etc...


I know it doesn't really apply to the problems in this thread, but belongs in any discussion of richness problems for later search results.

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